The present invention relates to a method for recycling plastic purge wherein flowable purge is received directly from a plastic molding machine and compressed into a form suitable for recycling.
In the injection molding of plastic material the initial start-up of the injection molding process typically involves bringing the plastic to the correct plasticity while simultaneously bringing the mold to the correct temperature. To bring the plastic to the correct plasticity, plastic must often be forced through the injection barrel of the plastic injection molding machine several times before the correct plasticity is achieved. The plastic ejected from the injection barrel during these initial runs cannot be used to mold plastic parts because of the incorrect plasticity. Furthermore, the plastic cannot be immediately reprocessed through the injection barrel because the plastic is no longer in a form suitable for reinjection. Although the plastic may be allowed to harden and then reground into pellets in a large scale grinder, this procedure is often not done due to the small amount of plastic recovered and the large amount of time involved in transporting the hardened purge to a large scale grinder. Typically, the purge is allowed to fall on the floor of the work area and harden. The purge is later removed and typically thrown away to end up in an incinerator or landfill. Although purge droppings are generally only about one to five pounds in weight, each molding machine may produce two or three purge droppings per run and may be involved in ten or more runs per day. Given that a typical plastic molding plant has several plastic molding machines in operation, the amount of purge droppings produced can become fairly significant adding up to increased cost as well as the increased detrimental effect to the environment of having such droppings disposed of in a landfill or incinerated.
The prior art method of recycling such droppings involves the transportation of such droppings to a large scale grinder which grinds the droppings up into pellet size portions which may then be reused in the injection molding process. Because the droppings are so large and of such an irregular shape, small pelletizers available at most plastic injection molding plants are not capable of handling such large irregular portions of plastic. The droppings must, therefore, be collected, cleaned of any debris, shipped to a large material grinder, pelletized in the grinder, repackaged, and returned to the plant for reprocessing. Rarely does the value of the pellets returned from this procedure outweighed the cost of the procedure itself. Because of this inefficiency, droppings are typically thrown away and not recycled.